Defects, Diffusion and Dopants in Li8SnO6

Octalithium tin (IV) oxide (Li8SnO6) is an important electrode material considered for lithium ion batteries (LIBs) because of its high lithium content. We employed atomistic simulations to examine the intrinsic defects, diffusion of Li-ions together with their migration energies and solution of potential dopants in Li8SnO6. The most thermodynamically favourable intrinsic defect is the Li Frenkel which increases the concentration of Li vacancies needed for the vacancy mediated diffusion of Li-ions in Li8SnO6. The calculated activation energy of migration of Li-ions (0.21eV) shows that the Li-ion conductivity in this material can be very fast. Promising isovalent dopants on the Li and Sn sites are Na and Ti, respectively. Doping of Ga on the Sn site can facilitate the formation of Li interstitials as well as oxygen vacancies in Li8SnO6. While the concentration of Li interstitials can enhance the capacity of this material, oxygen vacancies together with Li interstitials can lead to the loss of Li2O in Li8SnO6

Simple biophysics underpins collective conformations of the intrinsically disordered proteins of the Nuclear Pore Complex

Nuclear Pore Complexes (NPCs) are key cellular transporter that control nucleocytoplasmic transport in eukaryotic cells, but its transport mechanism is still not understood. The centerpiece of NPC transport is the assembly of intrinsically disordered polypeptides, known as FG nucleoporins, lining its passageway. Their conformations and collective dynamics during transport are difficult to assess in vivo. In vitro investigations provide partially conflicting results, lending support to different models of transport, which invoke various conformational transitions of the FG nucleoporins induced by the cargo-carrying transport proteins. We show that the spatial organization of FG nucleoporin assemblies with the transport proteins can be understood within a first principles biophysical model with a minimal number of key physical variables, such as the average protein interaction strengths and spatial densities. These results address some of the outstanding controversies and suggest how molecularly divergent NPCs in different species can perform essentially the same function

Organization of the Six-Cylinder Tractor Diesel Working Process

The purpose of the work is the organization of the six-cylinder diesel engines (with a power of 116 and 156 kW) working process with exhaust gas recirculation. The following systems and components were used in the experimental configuration of the engine: Common Rail BOSСH accumulator fuel injection system with an injection pressure of 140 MPa equipped with electro-hydraulic injectors with 7-hole nozzle and a 500 mm3 hydraulic flow; direct fuel injection system with MOTORPAL fuel pump with a maximum injection pressure of 100 MPa, equipped with MOTORPAL and AZPI five-hole nozzle injectors; two combustion chambers with volumes of 55 and 56 cm3 and bowl diameters of 55 and 67.5 mm; cylinder heads providing a 3-4 swirl ratio for Common Rail system, 3.5-4.5 for mechanical injection system; recirculation rate was set by gas throttling before the turbine using original design rotary valve. The tests were conducted at characteristic points of the NRSC cycle: minimum idle speed 800 rpm, maximum torque speed 1600 rpm, rated power speed 2100 rpm. It is established: achievement of emission standards for the 116 kW diesel engine is possible with the use of direct-acting fuel equipment and a semi-open combustion chamber; on the 156 kW diesel - using the Low Cost type common Rail fuel supply system and an open combustion chamber

Next-to-next-to-leading order QCD analysis of the Gross-Llewellyn Smith sum rule and the higher twist effects

We present the next-to-next-to-leading order QCD analysis of the Gross-Llewellyn Smith (GLS) sum rule in deep inelastic lepton-nucleon scattering, taking into account dimension-two, twist-four power correction. We discuss in detail the renormalization scheme dependence of the perturbative QCD approximations, propose a procedure for an approximate treatment of the quark mass threshold effects and compare the results of our analysis to the recent experimental data of the CCFR collaboration. From this comparison we extract the value of the strong coupling constant $\alpha_{s}^{nnl}(M_{Z},\overline{\rm MS})= 0.115\pm0.001(stat)\pm0.005(syst)\pm0.003(twist)\pm0.0005(scheme)$. We stress the importance of an accurate measurement of the GLS sum rule and in particular of its $Q^{2}$ dependence.Comment: Latex 19 pages and 4 Postscript figures appended at the end of this fil

Frequency drift in MR spectroscopy at 3T

Purpose: Heating of gradient coils and passive shim components is a common cause of instability in the B-0 field, especially when gradient intensive sequences are used. The aim of the study was to set a benchmark for typical drift encountered during MR spectroscopy (MRS) to assess the need for real-time field-frequency locking on MRI scanners by comparing field drift data from a large number of sites.Method: A standardized protocol was developed for 80 participating sites using 99 3T MR scanners from 3 major vendors. Phantom water signals were acquired before and after an EPI sequence. The protocol consisted of: minimal preparatory imaging; a short pre-fMRI PRESS; a ten-minute fMRI acquisition; and a long post-fMRI PRESS acquisition. Both pre- and post-fMRI PRESS were non-water suppressed. Real-time frequency stabilization/adjustment was switched off when appropriate. Sixty scanners repeated the protocol for a second dataset. In addition, a three-hour post-fMRI MRS acquisition was performed at one site to observe change of gradient temperature and drift rate. Spectral analysis was performed using MATLAB. Frequency drift in pre-fMRI PRESS data were compared with the first 5:20 minutes and the full 30:00 minutes of data after fMRI. Median (interquartile range) drifts were measured and showed in violin plot. Paired t-tests were performed to compare frequency drift pre- and post-fMRI. A simulated in vivo spectrum was generated using FID-A to visualize the effect of the observed frequency drifts. The simulated spectrum was convolved with the frequency trace for the most extreme cases. Impacts of frequency drifts on NAA and GABA were also simulated as a function of linear drift. Data from the repeated protocol were compared with the corresponding first dataset using Pearson's and intraclass correlation coefficients (ICC).Results: Of the data collected from 99 scanners, 4 were excluded due to various reasons. Thus, data from 95 scanners were ultimately analyzed. For the first 5:20 min (64 transients), median (interquartile range) drift was 0.44 (1.29) Hz before fMRI and 0.83 (1.29) Hz after. This increased to 3.15 (4.02) Hz for the full 30 min (360 transients) run. Average drift rates were 0.29 Hz/min before fMRI and 0.43 Hz/min after. Paired t-tests indicated that drift increased after fMRI, as expected (p &lt; 0.05). Simulated spectra convolved with the frequency drift showed that the intensity of the NAA singlet was reduced by up to 26%, 44 % and 18% for GE, Philips and Siemens scanners after fMRI, respectively. ICCs indicated good agreement between datasets acquired on separate days. The single site long acquisition showed drift rate was reduced to 0.03 Hz/min approximately three hours after fMRI.Discussion: This study analyzed frequency drift data from 95 3T MRI scanners. Median levels of drift were relatively low (5-min average under 1 Hz), but the most extreme cases suffered from higher levels of drift. The extent of drift varied across scanners which both linear and nonlinear drifts were observed.</p

Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign

Abstract: In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M ⊙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87’s spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded

Coarse Grained Modeling of Intrinsically Disordered Protein Structures and Dynamics

Contrary to natively folded proteins, which often have a single stable 3D structure, Intrinsically Disordered Protein (IDP) structures dynamically fluctuate between many conformations. This complexity impedes their study and the understanding of their functions. Experimental techniques can probe aspects of the conformations, but often different techniques or conditions offer seemingly contradictory results. In this thesis, I use coarse-grained models and simulations to investigate the structures and dynamics of IDPs. One system I focus on is the Nuclear Pore Complex (NPC): a bidirectional selective gate for cargo traveling across the nuclear envelope of eukaryotic cells. A key functional component of the NPC is the layer of intrinsically disordered FG nucleoporins attached to the interior of the transport channel. Elucidating the mechanism of transport remains elusive due to the size and complexity of the NPC, but will contribute to the understanding of diseases associated with mutations in the NPC, viruses which enter the nucleus via the NPC, and drug delivery into the nucleus, as well as the development of NPC inspired devices for nanotechnological applications. I show how a mean field model for surface grafted FG nups reconciles several conflicting experimental observations and theories of transport. Due to a lack of unique structure, the influence of the amino acid sequence on IDP structures and dynamics is unclear. Various evidence points to the overall importance of general properties of the sequence rather than the atomistic details of the amino acids. Using coarse-grained simulations, I investigate how the effects of several key sequence properties on the polymer dimensions and end-to-end distance dynamics of IDPs. These results have implications for interpreting experimental measurements as well as developing appropriate models of IDPs.Ph.D

Effects of Sequence Composition, Patterning and Hydrodynamics on the Conformation and Dynamics of Intrinsically Disordered Proteins

Intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) perform diverse functions in cellular organization, transport and signaling. Unlike the well-defined structures of the classical natively folded proteins, IDPs and IDRs dynamically span large conformational and structural ensembles. This dynamic disorder impedes the study of the relationship between the amino acid sequences of the IDPs and their spatial structures and dynamics, with different experimental techniques often offering seemingly contradictory results. Although experimental and theoretical evidence indicates that some IDP properties can be understood based on their average biophysical properties and amino acid composition, other aspects of IDP function are dictated by the specifics of the amino acid sequence. We investigate the effects of several key variables on the dimensions and the dynamics of IDPs using coarse-grained polymer models. We focus on the sequence “patchiness” informed by the sequence and biophysical properties of different classes of IDPs—and in particular FG nucleoporins of the nuclear pore complex (NPC). We show that the sequence composition and patterning are well reflected in the global conformational variables such as the radius of gyration and hydrodynamic radius, while the end-to-end distance and dynamics are highly sequence-specific. We find that in good solvent conditions highly heterogeneous sequences of IDPs can be well mapped onto averaged minimal polymer models for the purpose of prediction of the IDPs dimensions and dynamic relaxation times. The coarse-grained simulations are in a good agreement with the results of atomistic MD. We discuss the implications of these results for the interpretation of the recent experimental measurements, and for the further applications of mesoscopic models of FG nucleoporins and IDPs more broadly

Blending control of the trolleybus traction and brake drives to enhance the braking efficiency of a vehicle

Widespread usage of emission free public transport is the preferred strategy in many cities to reduce a congestion and pollution from the road traffic. The trolleybus is a kind of urban public transport, i.e. a fully electric vehicle, which is considered as a promising tool to enhance the efficiency of public transport and to attain the goals of sustainable development and quality of city life. The operation control of service brake system and secondary brake system (the braking torque of traction electric motor) is realized with help of one pedal in the trolleybus. Thus, there are modes of the joint operation for these systems during the braking process. Authors focus on the development of rule-based algorithm for the blending control of traction electric motor and anti-lock braking system to enhance the overall braking efficiency of a vehicle. The mathematical model of the trolleybus braking dynamics was developed for this purpose. Test bench and ride tests on different road surfaces were carried out to determine the parameters of vehicle braking efficiency and to validate the developed mathematical model. The corresponding experimental data were used to analyse the efficiency of proposed rule-based strategy for the blending control of traction electric motor and anti-lock braking system of the trolleybus. As a result, the availability of proposed control algorithm is confirmed, which secures the required braking efficiency and provides a high braking stability of the vehicle